CVE-2026-100794

CRITICAL 9.6CVE-2026-100794 · Published 29/09/2026 · updated 19/10/2026

In short

CVE-2026-100794 is a CRITICAL (CVSS 9.6) vulnerability affecting firefox (mozilla), thunderbird (mozilla).
Chance of exploitation in the next 30 days (EPSS): 0.32%, higher than 25.1% of all vulnerabilities.
Fix: update to 153.4.0, 157.0.0, 140.17.0, 157.0 or later.

Package	Affected versions	Patched versions
firefox mozilla	`≥ 141.0, < 153.4.0≥ 154.0.0, < 157.0.0< 140.17.0`	`153.4.0157.0.0140.17.0`
thunderbird mozilla	`≥ 141.0, < 153.4.0≥ 154.0, < 157.0< 140.17.0`	`153.4.0157.0140.17.0`

Description

Sandbox escape due to incorrect boundary conditions in the Internationalization component. This vulnerability was fixed in Firefox ESR 153.4, Thunderbird 157, Thunderbird 140.17, Thunderbird 153.4, Firefox 157, and Firefox ESR 140.17.

References

bugzilla.mozilla.org/show_bug.cgi · Permissions Required
mozilla.org/security/advisories/mfsa2026-100 · Vendor Advisory
mozilla.org/security/advisories/mfsa2026-101 · Vendor Advisory
mozilla.org/security/advisories/mfsa2026-102 · Vendor Advisory
mozilla.org/security/advisories/mfsa2026-103 · Vendor Advisory
mozilla.org/security/advisories/mfsa2026-97 · Vendor Advisory
mozilla.org/security/advisories/mfsa2026-99 · Vendor Advisory

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Package

Affected versions

Patched versions

firefox

mozilla

≥ 141.0, < 153.4.0≥ 154.0.0, < 157.0.0< 140.17.0

153.4.0157.0.0140.17.0

thunderbird

mozilla

≥ 141.0, < 153.4.0≥ 154.0, < 157.0< 140.17.0

153.4.0157.0140.17.0

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